Electro-osmotic pumps are mechanically less complex than other pumps; typically they have fewer components, particularly fewer moving components. Small pumps are widely used both in ambulatory and in non-ambulatory drug delivery systems, including systems comprising a skin-adhered drug reservoir and pump. For example, skin-adhered insulin “pumps” are in use. Their pumps are often mechanical. Electro-osmotic pumps for drug delivery have been considered for 40 years or more, but none were sold.
Electro-osmotic pumps that are manufactured and sold are applied in compact bioanalytical systems and in heat pumps. In some of these, the pumps now drive liquids through long and narrow on-chip and off-chip capillaries and through miniature packed chromatographic columns. Pumps have been integrated in silicon chips and are part of lab-on-chip devices. While polymeric ion exchange membranes were used in the early pumps, the more recent pumps have ceramic membranes, particularly of porous silica, although porous silicon and aluminum oxide have also been used. Platinum electrodes, on which water is electrolyzed at the applied high voltages ranging from 3V to 400V, are usually used. Gas bubbles resulting from electrolysis, however, may interfere with the operation of the pumps. Electro-osmotic pumps having ceramic membranes and gas-evolving electrodes have been sold, for example, by NI (Nano Fusion Technologies, Tokyo). Fouling may occur during pump operation due, for example, to migration of ions from the electrodes to the pump's membrane.